SBOA602 November   2024 OPA593

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Current Booster, Push-Pull Topology Output Characteristics
    1. 2.1 Open-Loop Output Impedance
    2. 2.2 Minimizing Zero Crossover Distortion
  6. 3Various Current Booster Configurations
    1. 3.1 Complementary MOSFET versus BJT Current Booster Comparisons
  7. 4Stabilizing a Design for Power Amplifier Driving 1μF Capacitive Load (CL)
    1. 4.1 Op-Amp Driving Resistive Load
    2. 4.2 Op-Amp Driving Capacitive Load and Challenges
    3. 4.3 Open-Loop AC Stability Analysis - Compensating CL Effects Using DFC
    4. 4.4 Closed-Loop Stability Response - Small Signal Step Transient Analysis
    5. 4.5 Effects of Riso on Frequency Response in Dual Feedback Compensation
    6. 4.6 Summary of the DFC Technique
  8. 5Stabilizing the OPA593 and Darlington Current Booster for 1μF Capacitive Load
    1. 5.1 Open-Loop AC Stability Analysis - Composite Op-Amp Driving 1μF CL
    2. 5.2 Closed-Loop Stability Response - Composite Op-Amp's Step Transient Analysis
  9. 6Composite Amplifier's Effective BW and Step Time Response
  10. 7Test Bench Validation
  11. 8Summary
  12. 9References

Closed-Loop Stability Response - Small Signal Step Transient Analysis

The small-signal step transient simulation plot confirms that the DFC is stable in the closed loop, as shown in Figure 4-6. There is no output overshoot, and the design meets the timing requirements outlined in Table 4-2.

 The Compensated Closed-Loop Response: Step Transient Analysis in Driving 1μF LoadFigure 4-6 The Compensated Closed-Loop Response: Step Transient Analysis in Driving 1μF Load

The final validation step in the simulation involves a frequency sweep of the OPA593 with the current booster and analyzing the gain responses, as shown in Figure 4-7. If the AC gains increase with frequency near the -3dB point, it typically suggests that two poles are too closely spaced or overlapped. This phenomenon is discussed in the next section.

 AC Frequency Sweep of the Emulated PA Driving 1μF LoadFigure 4-7 AC Frequency Sweep of the Emulated PA Driving 1μF Load